Japanese Patent Application Publication No. 2009-279661 discloses a semiconductor wafer including a thick region with a greater thickness than that of its central region along its outer circumferential surface. Such a semiconductor wafer is a semi-finished product produced in a process of manufacturing a semiconductor element. In manufacturing of the semiconductor element, a semiconductor wafer having a uniform thickness is first prepared, and a partial structure of the semiconductor element is formed in its central region of the semiconductor wafer. Next, the central region of the semiconductor wafer is ground from one main surface side such that the semiconductor element has a desired thickness. At this occasion, in order to secure a strength of the semiconductor wafer, a region along the outer circumferential surface of the semiconductor wafer is left without being ground, and the semiconductor wafer having the above-mentioned thick region is thus manufactured. Thereafter, a remaining partial structure of the semiconductor element is formed in the central region of the semiconductor wafer, and the semiconductor wafer is diced such that individual semiconductor elements are cut out from the semiconductor wafer.
In the above-described semiconductor wafer, if the thickness of the semiconductor wafer is abruptly changed between the central region and the thick region, a high stress is likely to be generated at a boundary between the central region and the thick region, and the semiconductor wafer may be damaged. Regarding this point, in the semiconductor wafer described in Japanese Patent Application Publication No. 2009-279661, one or more slope surfaces are provided between the central region and the thick region, and the thickness of the semiconductor wafer is made to be gradually changed between the central region and the thick region.